1. Field of the Invention
The present invention relates to an optical switch of the moving fiber type.
2. Prior Art
A well known type of switch for optical fiber circuits is the moving fiber type, where two fiber portions are fixed to opposed fiber supports separated by a gap, the fiber portions extending along a fiber axis and having opposed fiber ends separated by a fiber gap. One or both supports are movable between a first position in which the fiber ends are aligned, so that light can cross the fiber gap, and a second position in which the fiber ends are out of alignment.
Although some switches of this type have lenses, the most compact and energy efficient switches of this kind simply use a fiber gap between polished ends of the fibers. This means that the movable support or supports must be capable of very precise movement, which is preferably achieved by the use of a flexible mounting for each movable support. Examples of U.S. patents showing this type of construction are the following:                U.S. Pat. No. 5,239,599, issued Aug. 24, 1993,        U.S. Pat. No. 5,727,099, issued Mar. 10, 1998, and        U.S. Pat. No. 5,757,991, issued May 26, 1998;        
All of these patents have Murray R. Harman as inventor.
In the later two patents, there is a symmetrical arrangement of opposed supports which are each flexibly mounted on a connecting member or housing, and which are each moved by a link connected to an operating means. In both cases the operating means is capable of pivotal movement relative to the optical fiber axis, and to the connecting member or housing, in order to cause relative movement between the fiber ends. In the '599 patent the operating means is a pivot member which is pivotally moved, about a shaft-like pivot, relative to a housing which connects the flexible mounts of the supports. In the '991 patent the connecting member which joins the flexible mounts of the supports is itself pivotal about a shaft, and the operating means here is, in effect, a stationary part of the switch which is connected to the supports by flexible links.
The '099 patent shows an example of a moving fiber switch in which only one of the supports is flexibly mounted.
It is usual for such switches to be made by fixing a single optical fiber along the surfaces of two supports and across the gap between them, and then cutting this fiber to form the fiber gap. If the fiber gap thus formed is larger than the ideal, it has in the past been difficult to adjust this. U.S. Pat. No. 4,759,597, which issued Jul. 26, 1988 to Lemonde, suggests a construction in which the gap is adjusted by use of a micro-manipulator holding a part of the switch, but when the gap has been adjusted this is fixed by welding parts of the switch together, after which no adjustment is possible.